[linux-lvm] Problem with UUID, vgscan, vgcfgrestore

[Diederick van Dijk]

On Tuesday 03 April 2001 08:23, you wrote:
> Diederick van Dijk writes:
> > On Monday 02 April 2001 23:00, you wrote:
> > > Diederick van Dijk writes:
> > > > I've a LVM of 8 physical volumes that I've created with LVM 0.9.1
> > > > beta 2. I've the know problem that vgscan reports that it can't find
> > > > my VG. So I upgraded to LVM 0.9.1 beta 6 (tools and kernel) and
> > > > runned on each physical disk a vgcfgrestore. Unfortunately I didn't
> > > > solve the problem. Attached is the output of the commands vgdisplay
> > > > -v and a pvdata -U for each physical disk. Debug logs a very huge so
> > > > I won't attach them.
> > >
> > > You can try the following (experimental) procedure to fix the UUIDs:
> > >
> > > Check each PV with "pvdata -PP /dev/hdX" to ensure it has a valid
> > > UUID assigned.  Also get the PV numbers (starting with 1) for each of
> > > the PVs.  Finally, check the pv_uuidlist_on_disk.base for each PV.
> > > It will normally be 6144, but it does not have to be.
> > >
> > > for each PV (in PV# order)
> > >   dd if=/dev/hdX bs=1 skip=44 count=128 >> /tmp/uuids
> > >
> > > This should create a file /tmp/uuids which has all of the PV UUIDs in
> > > it. Make sure there are as many UUIDs in the file ("od -a /tmp/uuids"
> > > is good) as you have PVs (8 in your case).
> > >
> > > Now, we want to write the UUID list back to the PVs so vgscan is happy:
> > >
> > > for each PV (in any order)
> > >   dd if=/tmp/uuids of=/dev/hdX bs=1 seek=<pv_uuidlist_on_disk.base for
> > > hdX>
> >
> > Unfortunately this doesn't work. I get on of=/dev/hda2 an invalid
> > argument. Can you write to a partition with dd ? Or has it to be a disk
> > such as /dev/hda ?
>
> Should work fine writing to /dev/hda2.  The only thing that _may_ be an
> issue is that we are not writing aligned sectors to the disk, but under
> Linux even the "raw" disk devices are buffered I/O.  I just tested the
> above commands under 2.2.18 and it worked fine and my VG is still alive.
>
> Can you send the exact command-line you are using?  Also useful would be
> pvdata -PP for each disk in the VG.  If you are sure you are using the
> correct command-line for dd, you could try running it under "strace" to
> see where it is getting -EINVAL from.
>
> Cheers, Andreas

Ok Andreas,

My current system is on kernel 2.4.2 with LVM support build into the kernel.
So I booted with a 2.2.18 kernel with no LVM support what so ever and
the dd commands worked fine. Then I booted with the 2.4.2 kernel again and
did a vgscan and this worked too ! I checked the UUID's on the PV's
with pvdata -U /dev/hdxx and the UUID lists are now as they have to be.
If guess that LVM support in the kernel and dd were in conflict. To check
that I will boot with a 2.4.2 kernel without LVM support and try the dd 
dd commands later on.

Thanks from a happy Diederick